The NexStar User's Guide - Excerpt from
Chapter 14
Buying a Used NexStar
Amateur astronomers generally take excellent care of their equipment. Buying
a used telescope is a good way to save substantial money while still getting the
scope of your dreams. Here are some things to check on a used NexStar.
- Look for any obvious damage. Even if the dents or scrapes do not seem to
have caused damage to any critical components, the impact that caused them may
have caused unseen damage.
- Check the surfaces of the mirrors/lenses for scratches or discoloration
that will impair optical performance.
- Try the scope out at night, checking for pinpoint star images and similar
inside and outside focus star patterns as discussed in Chapter 9. Keep in mind
that distorted patterns can be caused by poor collimation or inadequate time
to cool the optics. If you cannot check the optics at night, focus on a
distant object, looking for obvious defects. You can even check defocused
"star" patterns using sunlight reflected off a distant glass or metal object.
- Check the focuser motion - it should move easily with little backlash.
- Power up the scope and attempt an Auto Alignment. Insure the scope slews
smoothly to the alignment stars. Accept the given location of the two
alignment stars. Press the Tour button and select an object, pressing Enter to
GoTo the object. Again, observe whether the movement is smooth.
- Set the rate to 2 and focus on a star or distant object. Does the scope
move smoothly (although slowly) in all four directions?
If the scope checks out, consider the age and condition and compare to the
cost of a factory new telescope. With the number of NexStar telescopes sold
since their recent introduction, I expect the market for used models to be
substantial in the next few years. Personally, I would hesitate to purchase a
used telescope via the Internet or through the mail - there is often little
recourse if the telescope happens to be damaged - but if you can see and test it
in person, a used scope is often a great deal.
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